Quantize

Quantize operation converts a f32 tensor to a quantized (u8/s8) tensor. It supports both per-tensor and per-channel asymmetric linear quantization. Output data type is specified in output tensor data type. Rounding mode is library-implementation defined.

For per-tensor quantization:

\[\dst_{i} = round(\src_{i} / scale + zp)\]

For per-channel quantization, taking channel axis = 1 as an example:

\[\dst_{\cdots,i,\cdots,\cdots} = round(\src_{\cdots,i,\cdots,\cdots} / scale_i + zp_i), i \in {[0, ic-1]}\]

where \(ic\) is the number of channels.

Operation Attributes

Attribute Name	Description	Value Type	Supported Values	Required or Optional
qtype	Specifies which de-quantization type is used	string	per_tensor (default), per_channel	Optional
axis	Specifies dimension on which per-channel de-quantization is applied	s64	A s64 value in the range of [-r, r-1] where r = rank(src), 1 by default	Optional
scales	Scalings applied on the src data	f32	A f32 list (only contain one element if qtype is per_tensor)	Required
zps	Offset values that maps to float zero	s64	A s64 list (only contain one element if qtype is per_tensor)	Required

Execution Arguments

The inputs and outputs must be provided according to the below index order when constructing an operation.

Inputs

Index	Argument Name	Required or Optional
0	src	Required

Outputs

Index	Argument Name	Required or Optional
0	dst	Required

Supported Data Types

Quantize operation supports the following data type combinations.

Src	Dst
f32	s8, u8

@note This operation is to support int8 quantization model.